Grinding-machine.



No. 7|2,87l. Patented Nov. 4, I902.

0. S. WALKER.

GRINDING MACHINE.

(Applicnibn filed Aug. 12. 1901.

(No Model.) 4 Sheets$haet L ML/ 611444014 Jmmm 4%7/Z/K W i (2%, KW

allow.

Patented Nov. 4, I902.

0. S. WALKER.

GRINDING IACHINE.

(Appliclinn Med Aug. 12, 1901.)

4 Sheets-Sheet 2.

(No Model.)

we uonms PcTzls co. MYO-LITHOq WASHINGTON, n. c. I

Patented Nov. 4, I902.

0. S. WALKER. snmnms cums.

A umianmed Aug. 12. 1901.1

4 Sheets-Shoot 3.

(No Model.)

2 0 mm 47 V o N d e t n e t a P on E K L A W S 0 H W 7 0 N GRINDINGMACHINE.

(Application filed Aug. 12. 1901.)

4 Sheets-Sheet 4.

(No Model.)

m: Nolals #(rzps co, momumo, wash UNITED STATES PATENT OFFICE.

OAKLEY S. \VALKER, OF \VORCFSTER, MASSACHUSETTS.

GRlNDlNGeMACHlNE.

SPECIFICATION forming part of Letters Patent N 0. 712,871, datedNovember 4, 1902.

Application filed August 12, 1901. Serial No. 71,737. (No model.)

f. *AAA 1 To all whom it may concern.-

Be it known that I, OAKLEY S. WALKER, a citizen of the United States,and a resident of Vorcester, in the county of Worcester and Commonwealthof Massachusetts, have invented a new and useful Improvement inGrindii1gMachiues, of which the following is a specification,accompanied by drawings forming a part of the same, in which- Figure 1is a side elevation with a portion of the column broken away to disclosethe chamber containing themotor for operating the carriage. Fig.Qisafrontelemtion. Fig. 3 is a detached view of the ratchet feedingmechanism for actuating the cross-feed. Fig. 4 is a central verticalsectional view on line 4 4, Fig. Fig. 5 is a detached view of theratchet feeding mechanism for actuating the cross-feed with theactuatiugpawls shown as moving the ratchets in the opposite directionsfrom that shown in Fig. 3. Figs. 6 and 7 are the front and side views,respectively, of the ratchet feeding mechanism with the pawls thrown outof engagement. Fig. Sis an enlarged front view of one of thecarriagedogs for actuating the reversing-switch. Fig. 9 represents insectional view portions of the carriage and platen supported thereonwith a portion of the actuating mechanism for i1n parting a feedingmotion to the platen. Fig.

10 is a transverse sectional view of the platen with a portion of itsactuating mechanism. Figs. 11 and 12 show, on a larger scale, de-

tails of the automatic stopping mechanisnr for stopping the cross-feedof the carriage. Fig. 13 is a partial front elevation of thereversing-switch. Fig. 14is a sectional view on line 14 14, Fig. 15.Fig. 15 is a rear view of the reversing-switch. Fig. 16 is a plan viewof the sliding bar for operating the reversing carriage 3, operated. bya cross-feed screw 4, journaled in a bearing 5, which is fastened to thecarriage 3 and engaging a fixed nut in the Fig. 18 is top 2 and providedwith a hand-wheel 6. The cross-feed screw 4 carries the right and lefthand hatchet-wheels 7 and 8, separated by an oscillating arm 9,journaled on the feed-screw 4 and carrying a stud 10, rotatably held inthe arm 9. Rigidly fastened to the stud 10 are two ratchet-pawls 11 and12, with their working ends on the same side of the vertical axis of thestud 10, so that each pawl will act as a weight to hold the other inengagement with the teeth of the ratchet-wheel.

1 :3 is a slotted sliding rest adjustably held by screws on the edge ofthe oscillating arm 9.

In Figs. 3 and 4 the rest 13 is in its lowest position, allowing thepawls 11 and 12 to be thrown to right or left into engagement with theirrespective ratchet-wheels.

In Figs. 3 and 4 the pawl 12 engages the wheel 8, and an oscillatingmovement of the arm 9 will rotate the feed-screw 4 in one direction, andin Fig. 5 the pawl 11 engages the wheel 7 and will move the feed-screw 4in an opposite direction, thus feeding the carriage 3 in or out, asdesired.

In Fig. 6 the slide 13 is in its upper position, and the pawls 11 and 12are represented as thrown to the left, with the pawl 11 in contact withthe rest 13 and holding the pawl 12 from engaging with the wheel 8,leaving the feed-screw 4 free to be turned by hand.

14 is the frictionally-driven disk, operated by the movement of themechanism inside the carriage 3 and capable of a free motion through apartial revolution untilit comes-in contact with a stop (not shown) andcauses a slipping action of its driving mechanism, which is of awell-known construction and in common use in metal planing and shapingmachines, and therefore not shown. The crank-disk 14 is connected by arod 15 with the oscillating arm 9, and the reason forstopping thecrank-disk 14 is to allow it to move more quickly at the beginning ofeach stroke of the platen and to stop any feeding action of the screw 4during the time that the grinding-wheel is operating upon the work, thefeeding action taking place after the work has passed under the wheeland before the beginning of the next out.

16 is a magnetic platen, and 17 the detachable magnetic polar face ofthe same. The magnetic platen is similar to that for which looselymounted on a pinion-shaft 33.

Letters Patent of the United States were granted me on the 28th day ofJanuary, 1902. This magnetic platen consists, briefly, of a centralupstanding rib or core Y, surrounded by a shell or casing y, the angularcontinuous space extending'between the core andlift the work to acertain degree. .The method, however, of applying an electric current tothis magnetic platen I believe to be novel and consists in attaching theterminals of the electric coil of the magnetic platen to the insulatedstrips or rods running longitudinally beneath the platen and fastenedthereto. The electric current is delivered to these terminal strips bymeans of insulated brushes I I, fastened in the carriage 3 in electricconnection with a dynamo and controlled by electrical devices to bedescribed later.

18 is an adjustable motor for the grindingspindle, details of which areshown in Fig. 17. 19 is the driving-motor for operating the magneticplaten and the feeding mechanism. It is held on a platform 20, which ishinged on trunnions 21, passing through holes in the base of the column1.

The weight of the motor 19 and the platform 20 may be supported by thedrivingbelt 22, connecting the motor with the driven pulley 23 on thegeared feed-shaft 24 in the carriage 3.

In Fig. 9 is shown the method of transmitting power from the motor bythe belt 22 to the shaft 24, which runs in a box 25 and is geared to ashaft carrying a worm 28 by the gears 26 and 27. The worm 28, which runsin oil, has its shaft extended and provided.

with a knob or wheel 29 for obtaining a fine adjustment of the platen byhand. 30 is a worm-gear driven by the worm 28 and is 31 is theplaten-driving pinion, which is fastened on the shaft 33 and engagestheplaten-rack 35, Fig. 10. The worm-gear 30 and pinion 31 are placedadjacent on the shaft 33, and they are shown coupled together by meansof the pin 32, fastened in the worm-gear 30, but hav ing a projectingend loosely fitting a hole in the pinion 31. The shaft 33, carrying thepinion 31, has considerable end play, and the shaft is provided at itsouter end with an external knob 34 for the purpose of moving the shaft33 longitudinally to connect and disconnect the pinion 33 and wormgear30. Mounted on the journal-box 25 is an insulating-block 36, to whichare attached the brushes I I, which deliver an electric current to thecoil in the magnetic platen 16 by their contact with the brass strips 44and 45, fastened to an insulating-block 37 beneath the magnetic 47, Fig.9, is an insulating-block fastened inside the carriage 3 for supportingthe electric wires which pass up through the slot 37 in the column-top 2to the binding-posts above mentioned.

The slot 38 in the column-top provides an opening for the driving-belt22, Fig. 9. Figs. 13, 14, 15, and 16 represent, on an enlarged scale,the reversing-switch,which is supported by a flange 5 ofthe feed-screwbearing .5 on the front of the carriage 3. The flange 5 is recessed uponits inner face for the reception of an insulating-block 48, preferablyof vulcanized fiber and attached to the flange 5 by screws. (Not shown.)

Upon the block 48 is pivotally mounted the switch-fingers 49 and 50,swinging on pins 51 and 52, projecting from metal plates 53 and 54,which are attached to the insulatingblock 48. Below the plates abovementioned and also fastened tothe insulating-block 48 are contact-plates55,56, and 57. The plates 53, 54,55, 56, and 57 correspond electricallyto the contact-points D, E, G, H, and G in regular order, as shown inFig. 1. The plates 55, 56, and 57 also have projecting pins 58, oneofwhich is shown in detail in Fig. 14, together with its binding-post 42in section, and an insulating-bushing 59 between the binding-post .andthe carriage 3. The pin 58 has a sliding electric contact in a recess inthe binding-post 42, as shown, and all the above-mentioned pins havesimilar connections with other binding-posts, the positions of whichareindicated by 39, 40, 41, and 43 in Fig. 9, where is also shown a wire41 connecting electrically posts 41 and 43. The electric current isdelivered to and received from the reversing-switch through thebinding-posts 39 and 40 and by their respective pins 51 and 52 iscommunicated through the switch-fingers 49 and 50. It will also be seenthat by means of the sliding contact of the pins with the binding-poststhe bearing 5 and flange 5 can be removed at any time without disturbingthe wiring. Coiled springs, one of which is shown at 60, Fig. 14, pressthe switch-fingers 49 and 50 against the plates 53 and 54 and alsoinsure the contact of their lower ends with the contact-plates 55, 56,and 57.

In Fig. 1 I have shown a diagrammatic arrangement at one side of thesupporting-column 1 of the system of wiring and of the relative positionof the contact-points made by the plates 53, 54, 55, 56, and 57, whichare in Fig. 1 represented diagrammatically by the contact-points D, E,G, H, and G, respectively. The switch-fingers 49 and 50 are in permanentcontact with the plates 53 and 54: and correspond with thecontact-points D and E, respectively.

Referring to Fig. 1, the point D, corresponding to the switch-finger L9,is connected to the armature-terminals A of the motor 19 by the wires 0'C and the point E is connected to the other armature-terminal A by awire L through the rheostat A so that as the switch-fingers 49 and 50swing from side to side they make electrical connections alternatelywith the field-terminals F F of the motor 19, which are electricallyconnected with the contact-points G, H, and G, corresponding with thecontact-points 55, 56, and

57, causing the motor 19 to rotate in either direction and by means ofits operative connection with the platen 16 cause it to move back andforth according as the switch-fingers are moved.

The switch is automatically operated as follows: The upper ends of theswitch-fingers 49 and 50 are connected by an insulating-bar 60, fromwhich project short pins 61, passing through holes in said fingers. Theinsulating-bar is operated by the sliding bar 62, which has lugs 62embracing each end of the bar 60, as shown in Fig. 16. A slot is formedin the flange 5 for the reception of the sliding bar 62, one side ofwhich enters the slot in the flange and embraces the bar 60, and theopposite side of the bar 62 is provided at its ends with projecting lugssupporting a rod 63, which passes through a lug 65, depending from areciprocating slide 66, which is operated by dogs 67 and 67, adjustablyattached to the platen l6 and moving the slide 66 in either direction asthe platen reciprocates. The rod 63 carries a pair of spiral springs 64and 64 between the lug 65 and the projecting lugs of the sliding bar, sothat the reciprocating movement of the slide 66 serves to alternatelycompress the springs 64: and 64, by which stored energy is obtained toassist in carrying the switch-fingers past their central position and ayielding connection is secured between the driving-lug 65 and the bar66, thereby overcoming a part of the momentum of the moving parts. Ithas been found in practice that when the platen is moving very slowlythe springs 64 and 6t do not always throw t he switch-fingers past theircentral position and destructive arcing occurs. To obviate this, Iattach to the rear side of the flange 5, Figs. 13, 14, and 15, a magnet70, held by the screws 71 and insulated by the packing 72. The poles ofthis magnet project past the ends of the sliding bar 62 with exactlysufficient clearance to allow for the reciprocating movement of thesliding bar, which comes in contact with the magnet at the end of eachmovement, the attraction of the magnet serving to prevent a rebound ofthe bar 62 and holding it against reverse movement until the springs 6%are suificiently compressed to throw the switch -fingers to theirextreme position.

Referring to Fig. 17, the grinding-spindle motor 18 is recessed at thebase for the reception of a field-piece 87, which in turn projects intoa sleeve 88, to which it is fastened by screws, (not shown,) thusproviding a detachable motor that may be replaced, by another at anytime, or a belt-driven spindle maybe mounted in its stead. The sleeve 88is held in an aperture in the split post 89 and can be clamped thereinat pleasure bya bolt in the clamping-lugs 90. The grinding-spindle 102of the motor is adapted to have secured to the opposite ends thereof adiskshaped or regular surface-grinding wheel 103, and the cuppedgrinding-wheel 99, respectively, and the head in which is carried thespindle 102 and motor 18 may be rotated in the sleeve 88 to bring eitherwheel to bear upon the surface to be operated upon. To the bottom of thesleeve 88 is fastened a nut 91, recessed for the coil-spring 92, whichimpinges on a second nut 93, held from independent rotation by the pin94, connecting the nuts 91 and 93. The lower end of the post 89 isprovided with a hollow hub, forming a journalbearing for a verticalfeedscrew 95, fitted with a beveled gear at its lower endand operated bya beveled gear 98, shaft 97, and hand-wheel 96. The tension of thespring 92 is greater than the weight of the motor 18, connected thereby,and its tension serves to press the nuts 91 and 93 apart and exert apressure on opposite sides of the threads of the feed-screw 95, and allslack motion is thereby obviated.

Fig. 8 represents, on alarger scale,one of the dogs 67, adj ustablyattached to the platen 16 in aT-slot and clamped by the bolt 69 and nut69. Pivoted loosely in a groove 68 in the under side of the dog 67 is alever 68,with itsinner end normally in position to strike the end of theslide 66 as the platen reciprocates and operate the reversing-switch.When it is desired to obtain temporarily a longer movement of theplaten, the lever 8 is swung by hand to the position shown by the brokenlines 68", in which position it passes over the slide 66. \Vhen eitherof the levers 68 are raised, the movement of the platen is limited bymeans of pins 115, (shown in Fig. 2,) projecting from the under side ofthe platen and arranged to strike the slide 66 and operate thereversing-switch.

I provide an automatic stop for the crossfeed of the machine, asfollows: To one side of the column 1 I attach an insulating-block B.(Shown in Fig. 1 and on a larger scale in Figs. 11 and 12.) Through theblock B, I pass the electric wires L, L", and L and through the top endof the block B a stop-rod 75 passes, held rigidly and adjustably at oneend by a bracket 74, attached to the carriage 3. The

rod 75 slides loosely through a hole in the block B and carries a pairof adjustable stop- ICC the circuit.

collars 76 76, coil-springs 77 77, and the insulating-washers 78 78,Figs. 11 and 12. On opposite sides of the block B and near its upper endare fastened the metal plates 79, 80, 81, and 82. The plates 79 and 80have mutual electric connections, and also the plates 81 and 82. To theplate 81 is attached a spring contact-plate 83, normally out of contactwith plate 79, as shown in Fig. 12, but which can be brought intocontact therewith by means of the washer 78 and spring 77 and stop 76when the rod is moved toward the right. To the plate 82 is attached aspring contactplate 84, which similarly is brought into contact with theplate by means of the washer 78, spring 77, and collar 76 when the rod75 is moved toward the left. The rod 75 is carried by the carriage 3,and the springs 77 77 provide a yielding pressure between the collars 7676 and plates 83 and 84. As the rod 75 is moved to the left plates 80and 84 contact and when moved to the right plates 79 and 83 contact, ineach case making a short circuit across the wires L and L as shown byFigs. 11 and 12, thereby weakening the force of a magnet L Fig. 1, whichis placed in the circuit of the electric wires L and L and as the forceof the magnet L is employed to hold a spring-actuated switch-lever L inoperative position to close the circuit to the motor 18, as hereinafterdescribed. The weakening of the magnet L allows the spring N of theswitch-lever L to operate and break The electric current enters themachine through the wire L, passes through a switch K and theinsulating-block B to the contact-lever L of the starting-rheostat L(shown in Fig. 1) in the out-of-contact position. The purpose of thisautomatic stop is to break the operative circuits, which furnish theprimary impulses to the actuating mechanism of the machine, and as aresult thereof to stop all Work performed thereby. For instance, theautomatic stop mechanism is set to break the operative circuits afterthe grinding-disk has passed over and operated upon twoinches, say, ofthe work undergoing treat ment, either for inspection by the operator orbecause a shoulder is to be or has been formed on the piece of work atsuch a distance from the edge. The carriage 3 is fed transversely of thelength of the machine by means of the ratchet-wheels 7 and 8 and pawls11 and 12 in the manner hereinbefore stated, and as it is fed forwardthe rod 75 is forced to the left in Fig. 12, let us suppose, owing toits rigid connection 74 with the carriage, until the contact-spring 84:is forced against plate 80, which will deflect a portion of the currentflowing through wires L L", as before set forth, which practically hasthe effect of throwing more resistance into the circuit and weakening itto such an extent that the magnet L is unable to retain the switch-arm Lagainst the tension of spring N, which latter now operates to withdrawthe leverarm to its limit of movement in one direction, breaking thefinally rests on the contact-point L operative circuits, but making theindependent bell-circuit to call attention to the fact that the enginehas stopped. This is a great advantage, as the operator, who generallyhas a number of machines to attend to, can set the work in position,adjust the automatic stopping mechanism to operate when a desired amountof the work-surface has been ground, start the machine, and then attendto other machines or other work, well knowing that he will receive duenotice when the machine has operated upon the necessary amount ofwork-surface, and can then return to it for an inspection of the workand to reset the machine. As the lever L is moved downward it makeselectric connections with variable-resistance contact-points L until itThe electric current by means of suitable Wiring now branches in threedirections, a portion going by two paths back to operate the motor 18and the third portion to operate the feed motor 19. The latter coursewill be traced first. From L the current is led to 0, when it againbranches, one portion passing to the right through a wire 0 and anotherportion to the left through a wire C The current through 0 passes to thearmatureterminal A of the motor 19, thence through the armature to A,thence to the variable rheostat A through which it passes to the wire L,through the switch K to the supply-main, and thus completes one electriccircuit through the armature of the motor 19. The current that passesthrough the wire 0 is led to the reversing-switch, (diagrammaticallyshown by the contact-points D, E, G, and H in Fig. 1,) the arrow-pointsindicating the swinging switch-fingers moved in unison, as heretoforeexplained, and alternately making electric connections D to H, E to G,and D to G, E to H, reversing the motor 19 by changing the relativeconnections between its field and armature terminals. The electriccurrent from wire 0 passes, Fig. 1, from D to H, thence to F, one of thefield-terminals of motor 19, thence through the field-coils to F, thenceto G and G, thence to E and to the wire L, completing a second electriccircuit through the fields of the motors 19. The electric current fromthe wire 0 also branches at D and passes to the brush I of the magnetictable 16, thence through the coils of the magnetic platen to the brush1, thence to E and L, completing a third electric circuit. Returning nowto point L of the starting-rheostat L the course of the current to themotor 18 is as follows: From the contact-point L the electric currentpasses to the armature of the motor 18 and through its armature and theswitch K to the return-wire L, completing a fourth electric circuit. Theelectric current from L also flows back through the resistance-points Lthence-to the wire L to the automatic release magnet L thence throughthe coils of this magnet to the variable rheostat F through the same tothe wire L thence to one of the field-terminals of the motor 18 throughits field-coils, and finally through the switch K to join thereturn-wire L and complete a fifth electric circuit. Inside the column 1I place an electric battery, (not shown,) wires to and from which leadthrough holes J and J in the column-top 2. A battery-wire passingthrough J connects with the arm L and separate contact, thence throughwire J to the electric bell J, thence through the hole J to theaforesaid battery, forming an independent circuit for ringing thealarm-bell J whenever the lever L is in the position shown in Fig. 1,lever L in this position resting on a separate contact-point connectedto wire J. The starting-rheostat L is of the well-known no-load releasetype, the lever L being thrown into the position shown in Fig. 1 by thetension of the spring N whenever the magnet L is demagnetized, thuscutting out all electric circuits on the machine and bringing themachine to a state of rest, at which time an alarm is rung by the bell Jto notify the operator.

It will be seen from the foregoing that when the lever I? of therheostat L is swung into position in electric connection with thecontact-points L the motor 18 is energized and at the same time themotor 18 automatically starts the motor 19, the platen 16 starts inmotion, and the magnetic force of the platen also is automaticallybrought into action, and when the electric supply fails for any cause orwhen contact is made between plates 83 and 79 or plates 84 and 80, Fig.12, there by weakening the magnet L the machine automatically stops.

To guard against the danger of grinding the work too thin by a carelessoperator, I provide the adjustable safety device shown in Fig. 18, inwhich 103 is the regular snrface-grinding wheel and 17 a portion of themagnetic face of the platen. A hole is drilled in one side of the platennear the edge for the reception of the internally-threaded stud 104,held in place by the thumb-screw 105. A spring 106 in the bottom of thehole tends to eject the stud when the screw 105 is loosened. Tightlyfitting the internal screwthread of the stud 10; is the screw 107,slotted in the usual manner for a screw-driver and fitted with a hardcarbon point 108. The screw 107 is adjusted to bring the carbon point108 at the height corresponding to the finished surface of the work tobe ground. As the platen having the work is moved under thegrinding-wheel, the latter first encounters the carbon point 108, and iffor any reason said Wheel has been lowered too far as the carbon passesunder it acts as a turning-tool and dresses the wheel to the proper sizeto suit the work, so that it becomes impossible to grind the same lowerthan the said carbon point. It is evident that this safety device couldbe applied to the edge of the platen-top 17 and perform its functions onthe cupped grinding-wheel 99 in the operation shown in Fig. 17. Thesupporting-post 1 is mounted on three wheels 109, 110, and 111, the twolatter turning loosely on trunnions at each side of the column 1, andthe wheel 109 is a caster-wheel swiveled in a bracket 112, bolted to therear side of the column 1. The upper end of the bracket 112 is tappedfor the reception of the adjusting thumb-screw 113, which impinges onthe end of the swiveled stem of the caster-wheel, which has anadjustable end movement and can be depressed until the rear of thecolumn 1 is raised from the floor, as shown in Fig. l, and the machinemoved to suit the convenience of the operator.

What I claim as my invention, and desire to secure by Letters Patent. is

1. In a grinding-machine, the combination of a grinding-wheel spindle,means for rotating said spindle,a reciprocating platen, means forreciprocating said platen comprising an electric motor, and means forautomatically reversing said motor controlled by the movcment of saidplaten, substantially as described.

2. In a grindingnnachine, the combination with a reciprocating platen,and an electric motor for driving said platen, of a switching mechanismby which the electric current to said motor is controlled, and means forautomatically operating said switch as determined by the movement ofsaid platen,substantially as described.

3. Ina grinding-machine, the combination of the reciprocating platen, anelectric motor for driving said platen, a switch by which the electriccurrent to said motor is controlled, and a pair of dogs adjustablyattached to said platen and arranged to operate said switch to reversesaid motor,snbstantiallyas described.

4. In a grinding-machine the combination of a motor for driving theplaten, a reciprocating platen driven by said motor, a switch forreversing said motor, adjustable dogs carried by said platen andarranged to operate said switch and pins held in said platen andarranged to operate said switch when the dogs are out of operativecontact therewith, substantially as described.

5. In a grinding-machine the combination of a reciprocating platen, anelectric motor by which said platen is driven, a switch by which thecurrent to said motor is controlled, and means determined by themovement of the platen for reversing said switch and comprising ayielding spring-actuated member, whereby the pressn re required toreverse the switch is temporarily stored, substantially as described.

0. In a grinding-machine, the combination of a reciprocating platen, anelectric motor for driving said platen, a switch for controlling thecurrent to said motor, a sliding bar by which said switch is operated,and means IOO for applying a yielding'pressure to said sliding bardetermined by the movement of the platen, substantially as described.

7. The combination with an electricallyrs'driven platen, of areversing-switch and a magnet by which the movement of the switch isretarded, substantially as described.

8. The combination with a reciprocating platen and an electric motor formoving said platen, of a sliding bar by which said switch is reversed,means for applying a yielding pressure to said bar and a magnet by whichsaid bar is temporarily held at the beginning of its movement,substantially as described.

9. In a grinding-machine, the combination with a hollowsupporting-column, a reciprocating platen held thereon, a motor by whichI said platen is reciprocated, abelt connection i between said motor andthe platen-actuating mechanism and a swinging platform supporting saidmotor, whereby the weight of the motor is utilized to hold said beltconnection taut, substantially as described.

10. Inagrinding-machine,thecombination of a reciprocating platen, anelectric motor for driving said platen, and means for automaticallybreaking the circuit to said motor, substantially as described.

11. Inagrinding-machine,thecombination of a grinding-wheel, an electricmotor for rotating the same, a reciprocating platen, an electric motorfor driving said platen, an electric circuit including both of saidmotors and means for automatically breaking said circuit, substantiallyas described.

12. Inagrinding-machine,thecombination of a grinding-wheel, an electricmotor for said wheel, a reciprocating platen, an electric motor for saidplaten, an electric coil inclosed in said platen, an electric circuitincluding said motors, and said platen-coil and means for automaticallybreaking said circuit, substantially as described. g

13. In agrinding-machine, the combination of a reciprocating platen, anelectric coil in closed in said platen, whereby said platen is renderedmagnetic, insulated contact-strips carried by said platen andelectrically connected with said coil and brushes forming the terminalsof an electric circuit held in contact with said contact-strips,substantially as described.

14:. In a grinding-machine, the combination with one or more motors foractuating the operative parts of the machine, of a suitable lever formaking and breaking a circuit, a magnet for holding said lever inposition to close said circuit, a spring acting to draw said lever awayfrom said magnet and means automatically actuated by the operative partsof the machine for varying the energy of said magnet to effect a releaseof said lever and break the circuit, substantially as described. 15. Inagrinding-machine, the combination of a grindingwheel, a reciprocatingplaten, a motor for driving said platen, a motor for driving saidgrinding-wheel, an electric circuit including said motors, independentcontacting members whereby said electric circuit is short-circuited andmeans forautomaticall y making said contact, substantially as described.

Dated this 29th day of July, 1901.

OAKLEY S. WALKER.

ANDREW J. DEWEY.

